U.S. patent application number 12/531500 was filed with the patent office on 2010-05-06 for distance holder with helical slot.
Invention is credited to Jan-Jette Blange.
Application Number | 20100108389 12/531500 |
Document ID | / |
Family ID | 38323972 |
Filed Date | 2010-05-06 |
United States Patent
Application |
20100108389 |
Kind Code |
A1 |
Blange; Jan-Jette |
May 6, 2010 |
DISTANCE HOLDER WITH HELICAL SLOT
Abstract
A distance holder for connection to, and rotation with, a drill
string in an earth formation drilling device arranged to supply a
jet of abrasive fluid for the purpose of providing a borehole by
removing earth formation material through abrasion, comprises a
housing with a chamber which is essentially rotational symmetric
and which is to face the earth formation material, and a jet nozzle
which arranged for discharging a jet of the abrasive fluid in the
chamber, the housing comprising at least one slot for allowing the
abrasive fluid to leave the chamber. The slot is continued over the
housing outer surface so as to counteract rolling motions of the
particles which are comprised in the abrasive fluid.
Inventors: |
Blange; Jan-Jette;
(Rijswijk, NL) |
Correspondence
Address: |
SHELL OIL COMPANY
P O BOX 2463
HOUSTON
TX
772522463
US
|
Family ID: |
38323972 |
Appl. No.: |
12/531500 |
Filed: |
March 20, 2008 |
PCT Filed: |
March 20, 2008 |
PCT NO: |
PCT/EP08/53341 |
371 Date: |
September 16, 2009 |
Current U.S.
Class: |
175/54 |
Current CPC
Class: |
E21B 21/002 20130101;
E21B 7/18 20130101 |
Class at
Publication: |
175/54 |
International
Class: |
E21B 7/16 20060101
E21B007/16; E21B 7/18 20060101 E21B007/18 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 22, 2007 |
EP |
07104677.5 |
Claims
1. A distance holder for connection to, and rotation with, a drill
string in an earth formation drilling device arranged to supply a
jet of abrasive fluid for the purpose of providing a borehole by
removing earth formation material through abrasion, comprising a
housing with a chamber that is essentially rotationally symmetric
and which faces the earth formation material, and a jet nozzle
arranged for discharging a jet of the abrasive fluid in said
chamber, said housing comprising at least one slot for allowing the
abrasive fluid to leave the chamber, wherein the slot is continued
over the outer surface of said housing, and wherein the housing at
its axially outermost end comprises a skirt, the slot being
provided in said skirt, wherein in that the slot extends helically
on the outer surface of the skirt.
2. The distance holder according to claim 1 wherein the slot
comprises an interruption of the skirt, a helically extending part
of the slot connecting to said interruption.
3. The distance holder according to claim 1 wherein the skirt has
outer cross sectional dimensions that are larger than the outer
cross sectional dimensions of the housing part adjoining said
skirt.
4. The distance holder according to claim 3 wherein the helically
extending part of the slot opens in the space delimited by the
outer surface of the housing part adjoining the skirt.
5. The distance holder according to claim 1 wherein the skirt is
provided with a deflector positioned in the path of the fluid jet
discharged from the jet nozzle.
6. The distance holder according to claim 5 wherein the deflector
adjoins the slot.
7. The distance holder according to claim 5 wherein the deflector,
when seen in circumferential direction, extends between an end
adjoining the skirt and an end adjoining the slot.
8. The distance holder according to claim 7, wherein the skirt has
an outer surface and an inner surface, and the distance of the
deflector near or at the end adjoining the skirt to the axis of
rotation is approximately the same as the radius of the slot inner
surface and the distance of the defector at or near the end
adjoining the slot has a distance to the axis of rotation which is
approximately the same as the radius of the slot outer surface.
9. The distance holder according to claim 5 wherein the deflector
comprises at least one plate.
10. The distance holder according to claim 5 wherein the deflector
comprises tungsten carbide.
11. The distance holder according to claim 5 wherein the size of
the deflector, when seen in circumferential direction, is
approximately the same as the width of the abrasive fluid jet at
the position of the deflector and issued by the jet nozzle.
12. The distance holder according to claim 1 wherein the chamber
has a trumpet-shaped inner surface.
13. The distance holder according to claim 12 wherein the
trumpet-shaped surface comprises a radially extending recess into
which the jet nozzle discharges.
14. The distance holder according to claim 1 wherein the jet nozzle
is oriented obliquely with respect to the axis of rotation for
making the jet of abrasive fluid intersect the borehole axis.
Description
PRIORITY CLAIM
[0001] The present application claims priority from
PCT/EP2008/053341, filed 20 Mar. 2008, which claims priority from
EP Application 07104677.5, filed 22 Mar. 2007.
BACKGROUND OF THE INVENTION
[0002] The invention is related to a distance holder for connection
to, and rotation with, a drill string in an earth formation
drilling device arranged to supply a jet of abrasive fluid for the
purpose of providing a borehole by removing earth formation
material through abrasion, comprising a housing with a chamber
which is essentially rotational symmetric and which is to face the
earth formation material, and a jet nozzle which arranged for
discharging a jet of the abrasive fluid in said chamber, said
housing comprising at least one slot for allowing the abrasive
fluid to leave the chamber.
[0003] Such a distance holder is disclosed in WO-A-2005/040546. By
means of an earth formation drilling device which is equipped with
a distance holder of this type, the borehole bottom is abraded by
the abrasive particles comprised in the abrasive fluid which is
discharged at high velocity. Due to the orientation of the jet
nozzle, a cone is formed on the borehole bottom. The abrasive fluid
hits said cone, abrading it further and further. The fluid is
discharged from the chamber through the slot, and subsequently the
fluid is urged to flow upwardly along the outside of the distance
holder into the annulus between the drill string and the borehole
wall. By means of a magnet contained in the earth drilling device,
the abrasive particles are extracted from the fluid and fed back to
the jet nozzle for further abrasive action.
[0004] However, the shape of the cone and the way in which the
fluid hits said cone, may impair the extraction of steel abrasive
particles. The steel abrasive particles show the tendency to roll
along the slope of the cone formed on the borehole bottom. The
rotational speed of these steel abrasive particles may well exceed
60,000 rpm in this way. The steel abrasive particles continue to
rotate at this high rotational speed while travelling upwardly
along the earth drilling device and in particular along the part
thereof containing the magnet.
[0005] The rotation of the particles has a tangential orientation.
The contacts of the rolling particle with the borehole wall further
induces the rotational effect with tangential orientation. Said
rotation of an abrasive particle that contains ferromagnetic and
electrically conducting material reduces the penetration of a
magnetic field into the particles. This causes a reduction of the
magnetic force exerted by the magnetic separator onto the steel
abrasive particles. For instance, in the case of steel abrasive
particles with a diameter of 1 mm, the loss of magnetic attraction
becomes significant. The combination of upward particle velocity
and rotational particle speed at the position of the magnetic
separator makes the magnetic field generated by the magnetic
separator less effective. Consequently, extraction of the steel
abrasive particles from the fluid is impaired.
SUMMARY OF THE INVENTION
[0006] The object of the invention is therefore to provide a
distance holder of the type described before which provides a
better extraction of the steel abrasive particles. Said object is
achieved in that slot is continued over the housing outer
surface.
[0007] The continuation of the slot over the outside of the housing
has several effects. Such slot first of all may impose a flow path
that is different from the flow path that is oriented vertically
upwardly. Instead the steel abrasive particles, which collide with
the borehole wall and the slot walls, may now be subjected to
rotational impulses of a different orientation than a tangential
orientation. In that case, such rolling effect with tangential
orientation will not be promoted but will be decreased.
[0008] Additionally, the path of travel of the steel abrasive
particles will generally become longer, depending on the shape
selected for the slot. Thereby, the rotating steel abrasive
particles will be subjected for a longer time period to the
decelerating drag effect of the fluid, which further reduces the
rotational speed thereof.
[0009] In practice, the invention can be carried out in several
ways. In case the housing comprises a skirt at its axially
outermost, the slot is provided in said skirt. The slot then
extends over the outside of the skirt. In a preferred embodiment,
the slot extends helically over the outer surface of the skirt.
Thereby, a dominant helical flow of the fluid and steel particles
is obtained, in combination with a relatively long way of travel of
said particles before reaching the magnetic separator. This
furthermore promotes the slowdown of the rotation and velocity of
the steel abrasive particles, and thereby an improved extraction
effect of the magnetic separator. After the rolling steel abrasive
particles hit the borehole bottom, they move radially outwardly. By
means of the slot, the flow is bending into the circumferential
direction.
[0010] The rotational speed and velocity of the steel abrasive
particles can be further reduced, at the location of the magnetic
separator, in case the kirt has outer cross sectional dimensions
which are larger than the outer cross sectional dimensions of the
housing part adjoining said skirt. The fluid flow, after leaving
the slot, is then entering a relatively wide space. This transfer
to a relatively wide space brings a reduction of the velocity,
which is beneficial for extracting the steel abrasive particles
from the fluid flow. Preferably, the skirt is provided with a
deflector positioned in the path of the fluid jet discharged from
the jet nozzle. By means of such deflector, the fluid can be
promoted to flow into the direction of the slot.
[0011] In this connection, the orientation of the deflector is of
importance. The effect of the deflector is enhanced in case said
deflector, when seen in circumferential direction, extends between
an end adjoining the skirt and an end adjoining the slot. Moreover,
preferably the skirt has an outer surface and an inner surface, and
the distance of the deflector near or at the end adjoining the
skirt to the axis of rotation is approximately the same as the
radius of the slot inner surface and the distance of the defector
at or near the end adjoining the slot has a distance to the axis of
rotation which is approximately the same as the radius of the slot
outer surface.
[0012] Furthermore, the size of the deflector, when seen in
circumferential direction, may be approximately the same as the
width of the abrasive fluid jet at the position of the deflector
and issued by the jet nozzle. Such dimension is appropriate for
deflecting the full abrasive jet in the desired direction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The invention will further be described with reference to an
example shown in the drawings.
[0014] FIG. 1 shows a side view (partially taken away) of the earth
drilling device according to the invention.
[0015] FIG. 2 shows the opposite side view.
[0016] FIG. 3 shows a view in perspective from below of the
distance holder.
[0017] FIG. 4 shows another view in perspective of the distance
holder.
[0018] FIG. 5 shows a bottom view of the distance holder.
[0019] FIG. 6 shows a schematic view of abrasive particle rolling
as occurring in prior art earth drilling devices.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0020] The earth drilling device 2 as shown in FIGS. 1 and 2 is
accommodated in a borehole 4 in an earth formation 5 and comprises
a distance holder 1 and a drill string (not shown), which together
are rotatable about an axis of rotation 3. Drill string 2 is
suspended from a drilling rig at the surface of the earth formation
5, and comprises a pressure conduit 6 by means of which a drilling
fluid is supplied to a jet nozzle 10, which is visible in the
partially broken away view of FIG. 1. The drilling device
furthermore comprises a magnetic separator 9 which consists of a
magnet 7 contained in a magnet housing 8.
[0021] Steel abrasive particles 11 are extracted from the drilling
fluid at the level of the magnetic separator 9. Under the influence
of the magnetic field of magnet 7 of magnetic separator 9, the
steel abrasive particles are attracted onto the surface of magnet
housing 8. As a result of the shape of magnet housing 8, which
tapers towards inlet 12 of jet nozzle 10, and the particular
magnetic field as generated by magnet 7, the steel abrasive
particles 11 on magnet housing 8 are drawn towards inlet 12 of jet
nozzle 10. Subsequently said steel abrasive particles are sucked
into said inlet by the underpressure which is generated in the
throat of the jet nozzle by the high velocity fluid.
[0022] Jet nozzle 10 discharges the drilling fluid mixed with steel
abrasive particles in the chamber 13, in particular in the recess
23 thereof. The chamber 13 is accommodated in the distance holder
housing 22 and has a trumpet-shaped upper part 14 and an
essentially cylindrical skirt 15. The fluid/particle mixture
generates a cone shaped downhole bottom 16. Thus, upon impact of
the drilling fluid/particle mixture on the slope of the bottom cone
16 the particles 11 may obtain a rotation with an axis which is
tangentially oriented in the downhole coordinate system. This
effect is schematically shown in FIG. 6, from which the distance
holder has been omitted. The speed of this rotation may well exceed
60,000 rpm. After attaining the lowest part of the bottom, the
direction of the steel abrasive particles is reversed in upward
direction whereby the tangential rotation plays a role as well.
[0023] When travelling further upwards, the rotating steel abrasive
particles 11 reach the magnetic field as generated by magnetic
separator 9. In prior art drilling devices, said field is unable to
penetrate the steel abrasive particles as a result of the high
rotational speeds thereof. Thus, extraction of the steel abrasive
particles 11 from the fluid is less successful, resulting in the
transport of large amounts of steel particles through the
circulation system of the fluid. This however is quite undesirable,
from a point of view of wear of the system. Moreover, the resulting
lack of abrasive magnetic particles near the bottom negatively
influences the forming of a hole.
[0024] According to the invention therefore, means have been
implemented which prevent the bypassing of high rotational velocity
steel abrasive particles past magnetic separator 9. These means
include a slot 18 having a helically shaped part 17, which slot 18
furthermore comprises a slot part 19 through which the
fluid/particle mixture leaves chamber 13. After abrading the earth
formation, said mixture reaches slot part 19 and is redirected
toward helical slot part 17, as shown in FIGS. 1 and 5. This change
of direction of the flow is promoted by the orientation of a
deflector 20, such as a plate of tungsten carbide. The distance D1
of said deflector 20 at its side bordering the slot part 19 to the
rotation axis 10 is larger than said distance D2 of said deflector
20 at its opposite side. The slanting orientation of the deflector
20 makes that the fluid/particle flow is diverted towards the slot
18, as shown in FIG. 5.
[0025] Along the flow path of slot 18, steel abrasive particles 11
collide with the walls bordering slot 18 as well as with the
borehole wall 4. Thereby rotations are generated with an axis that
is different from the original tangential rotation axis, as a
result of which the overall rotational speed of the steel abrasive
particles is reduced. Moreover, the length of the flow path of the
steel abrasive particles from the cone 16 up to the magnetic
separator 9 is increased appreciably. This means that the effect of
slowing down the rotational speed of said particles is also
increased as a result of drag forces generated by the fluid.
[0026] At the level of magnetic separator 9, the rotational speed
of steel magnetic particles 11 has reached such a low magnitude
that the extracting effect of the magnetic field of the magnetic
separator is restored. This is also achieved by the overall
decrease of the particle and fluid velocity that occurs as a result
of the wider annulus at the level of the housing part 21 of
distance holder housing 22. The outer diameter of housing part 21
is smaller than the diameter of skirt 15.
* * * * *